1. Field of the Invention
The present invention relates to a polling method and apparatus for a digital processing system. Particularly, it relates to a method for polling through an information collecting command transmitted from a control unit to a plurality of controlled units in order to collect status information from each controlled unit, and a polling apparatus for realizing the polling method in a digital processing system, particularly, a transmission apparatus in a digital communication system.
2. Description of the Related Art
In general, a transmission apparatus used in a digital communication system is formed by a supervisory control unit and a plurality of controlled units, and each controlled unit performs various processes, for example, switching control of redundancy portion, setting of status, collection of alarm signals, etc.. In order to perform these processes, it is necessary to perform polling operation from the supervisory control unit to each controlled unit by using a command from the control unit to each controlled unit and using status information from the controlled unit to the control unit.
In the above polling operation, it is always required to reduce polling time between the control unit and a plurality of controlled units, even if any one of controlled units is not mounted or has failed, or the controlled unit is normal, but an internal circuit thereof has failed.